Materials containing antifouling paints or other toxic substances were 

 excluded from exposure aboard the STU. The current velocity at a depth of 

 2,340 feet and 5,300 feet was not great enough (less than 0.5 knot) to carry 

 away any toxic substance which might alter the natural biological fauna found 

 in the immediate vicinity of the STU. 



RESULTS 



STU II-l Materials 



Test specimens on STU II-l (Test Site 2) recovered after 6 months 

 exposure on the ocean floor in 2,340 feet of water were examined for signs 

 of biodeterioration, fouling and boring organisms. Teredo-like molluscan 

 borers, Xylophaga washlngtona , were found boring into wood panels such as 

 pine, fir, ash, oak, maple and even redwood which is considered highly resistant 

 to insect and to decay damage. Some of the borers were about 1/8 inch in 

 diameter and had penetrated over 5/16 inch into the wood. These borers were 

 also found boring into plastic specimens such as acrylic, polystyrene, 

 cellulose acetate rods, vinyl tubes, and plastic electrical tape. 



Most of the borers were found boring into the solid plastic along the 

 edge of the plastic tape wrapping. Approximately 150 borer holes were 

 present around a 1-inch diameter acrylic rod along the edge of the plastic 

 tape wrapping. The depth of penetration was about 1/64 inch and the diameter 

 of these borers was about 1/32 inch. 



The borers i^jere also found over the entire length of two 5-foot Manila 

 rope specimens severing the fibers as they bored into the rope. There were 

 several hundred borers per lineal inch of the rope and it was estimated that 

 757„ of the tensile strength of the rope was destroyed. The fibers of cotton 

 rope and jute (burlap) wrapping were decayed by microbiological activity. 

 About 507„ of the tensile strength of 1/2-inch diameter cotton rope specimens 

 was destroyed. The nylon and polypropylene rope specimens were in good 

 condition. Silicone rubber insulation over electrical conductors exposed 

 on the sea floor were deteriorated by the nibbling and biting action, 

 possibly by the crabs and amphipods which were found on the bio-racks. In 

 some area of the insulation, the bare wire was exposed to the sea water. 



STU I-l Materials 



Teredo-like molluscan borers had also damaged plastic and wood 

 specimens exposed for 35 months at a depth of 5,300 feet in water at Test 

 Site 1. 



The damage to the above materials by the borers was very extensive as 

 compared to damage of materials recovered from a depth of 2,340 feet after 

 6 months exposure . 



170 



